Lemme put my 2 cents in. The the EE business there are a few ways to make things smaller and in this case, computer devices smaller. Granted digital electronics and microtronics isn't my subfield, but i do know how things work. Although you can PM Ikanayam if you want to know more lol since his field is dedicated to microprocessors.

Either way, the first way to make things smaller is markedly to cram more shite into a smaller area, which means more processors into a singular microprocessor. You don't use IGBTs for switches, FETS with individual logic cells are used. Anyways, but making the production process smaller and multileveled, you're essentially cramming more transistors into the same area, thus you can make smaller chips.

The limits of this are dependent on the materials used, the gate construction, the routing of the microwires and so on. But generally you get the picture lah.

Secondly, to cram more shit into stuff, you need to integrate more discrete components into the system, or increase route density so that more options exist when it comes to component placement. The easiest way is to stuff more conductive layers into a PCB (circuit board), so that routing becomes easier and the physical layout can have it's density increased.

Thirdly, you always have the problem of heat, cramming so much into such small areas always gives you a problem with heat. By adopting either lower powered components or adopting better cooling, technically, the component density around "hot spots" can be increased, giving you a smaller package by default.

Last if not least, no, the military does no possess better than consumer electronics technology. They usually follow DOD MILSTD when it comes to stuff like temp curve stability, shock reliability and so on. Meaning that it's no more advanced than normal stuff we use, but instead of having a transistor in a single ceramic plastic case, military components come in metal canned LMC style casings. Resistors also come in fireproofed coating and the higher spec RNXX series. The Military emphasizes it's technology towards hardened reliability and the ability to operate in differing environments, often they will choose to use battle toughened last generation technology rather than latest generation stuff.

Incorrect, the difference of spectrum has little to do with the electronic requirements of a device. I can build a simple device with parts scattered around my house that can transmit into the same frequency net as SINCGARS and other systems. They don't require special engineering by a longshot. Even the advanced battle laptops used are just specially binned Core2Duos with a hardened packaging and no more than that. Alot of the Engineers Australia and IEEE members i meet work for DSTO in developing Military technologies, and hey, it ain't all superweapons lol.

Actually 3D rendering, developed by the likes of Phong and so on, were developed in civilian labs. The military could use these methods due to the availability of computational power.

The Military has never been in the real business of cutting edge, it's in the business of winning wars, that's why foot soldiers are still using M4s instead of stuff like F2000s, SCARs or Magpul Masadas. Reliability is a huge issue.